#include<bits/stdc++.h>

using namespace std;
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;



typedef long long ll;
typedef long double ld;

#define endl "\n"
#define all(a) a.begin(), a.end()
#define pb push_back
#define eb emplace_back
// #define int long long



// Don't Start typing till you complete the idea.


// Check these things for WA and before submitting
// 1. Did you clear all the global arrays
// 2. Did you checked your <= >= < > 
// 3. Did you take the input properly. Did you use break or return while taking input?
// 4. Did you divide by 0.
// 5. Check array , vector , etc size
// 6. in the while loop did you miss something that would cause infinite loop?
// 7. Did you save your dp?
// 8. Are you trying to use something after deleting it?
// 9. Did you read the problem statement wrong?
// 10. Did you check the constrains of the problem properly
// 11. Did you checked for smaller cases like 1 , 0 , etc
// 12. Is it something to with overflow?
// 13. Did you initialized all the variables properly?
// 14. Did you use the formulas correctly?

// STRESS TESTING !!!!!! STRESS TESTING !!!!!
// STRESS Testing Not working?
// Stress test for multiple cases? 
// Stress test for big inputs?
// Stress test for really small inputs?
// Even then if it doesn't work -> Did you wrote the wrong Brute force code


// Check these things if you are not generating ideas
// 1. Did you try thinking it in reverse?
// 2. Read the problem statement again
// 3. Check the constraints again
// 4. Try smaller cases in notebook and try to expand
// 5. Think about invariants
// 6. Think simpler ideas maybe?
// 7. Think brute force and try to get something out of it.
// 8. Maybe take a deep breath and take a break for few minutes and drink some water? :3 
const int N = 1e6 + 3;
vector<int> adj[N];
struct custom_hash {
  static uint64_t splitmix64(uint64_t x) {
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }
  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
};
gp_hash_table<int, int, custom_hash> st[N];
int sz[N];
int small[N];
void dfs(int u , int p = 0){
  sz[u] = 1;
  int mnv = N;
  small[u] = -1;
  for(auto x : adj[u]){
    if(x == p) continue;
    dfs(x , u);
    sz[u] += sz[x];
    if(mnv > sz[x]) mnv = sz[x] , small[u] = x;
  }
  if(small[u] != -1) swap(st[small[u]] , st[u]);
  vector<int> bad;
  for(auto x : st[u]){
    for(auto y : adj[u]){
      if(y == small[u] || y == p) continue;
      if(st[y].find(x.first) == st[y].end()) {
        // cout << y << ' ' << small[u] << ' ' << x.first << endl;
        bad.pb(x.first);
        break;
      }
    }
  }
  for(auto x : bad) st[u].erase(x);
  st[u][sz[u]] = 1;
  // cout << u << endl;
  // for(auto x : st[u]) cout << x.first << ' ' << x.second << endl;
}

void GG()
{ 
  int n;
  cin >> n;
  for(int i = 1; i <= n; i++){
    adj[i].clear();
    st[i].clear();
    sz[i] = 0;
  }
  for(int i = 2; i <= n; i++){
    int x , y;
    cin >> x >> y;
    adj[x].pb(y);
    adj[y].pb(x);
  }
  dfs(1);
  cout << st[1].size() << endl;
  vector<int> lst;
  for(auto x : st[1]) lst.pb(x.first);
  sort(all(lst));
  for(auto x : lst) cout << x << ' ';
  cout << endl;
}

signed main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);

	int ttc=1;
	cin>>ttc;
	//int cnt=0;
	while(ttc--)
	{
		//cout<<"Case "<<++cnt<<": ";
		GG();
	}
}